A wide variety of automated chemical analyzers are known in the art and are widely used in hospitals, clinics, and research laboratories. A particularly popular example of such a device is the multi-channel type of analyzer in which a series of different tests are performed simultaneously and in parallel with one another. The typical multi-channel analyzer generally utilizes liquid or solid reagents to react with a particular constituent present in a sample to result in a change in transmissibility, absorption, color, photo-optical characteristic or other coligative electrical or physical property of the sample. In conjunction with the multi-channel analyzer, a photo-optical system and electro chemical detector means are employed to determine the rate of reaction, or concentration of the constituent in the sample, and the like.
The usual method employed for performing these photometric procedures is to place a portion or aliquot of the sample solution in a small cell, tube, or cuvette provided with transparent walls, and then to interpose the sample solution between a light source and a photosensitive detecting element or to flow the sample past sensors. In order to perform multiple tests simultaneously on each sample most contemporary multi-channel analyzers utilize a number of small sample aliquots taken from a larger sample volume or specimen originally supplied to the machine. These larger sample specimens are stored and manipulated in cells or tubes of varying size and configuration, the most common being round elongate sample or test tubes, while others include rectangular or square cells and alternative configurations. This form of individualized sample processing avoids the problem of cross-contamination of samples which could occur with the earlier flow-through type of analyzers.
Although multi-channel automated analyzers have received wide acceptance, there are certain drawbacks associated with their use. For example, to provide precise and accurate handling of the sample tubes it is necessary to position and align the tubes within the apparatus accurately so that the various sample aliquots may be automatically and consistently removed as needed. Additionally, in order to correlate the multiple test results properly with the appropriate samples an accurate identification and tracking system must be utilized. As a result, a variety of specialized sample cells and identification means have been developed in the art. Unfortunately, the majority are machine-specific, which limits the applicability of the particular analyzer to those samples which are packaged in the specific sample tubes or cells. Alternatively, some analyzers provide for the use of adapters for sample cells other than the one machine-specific design, which adapters unfortunately, can be clumsy and time-consuming to use. Also, relatively highly-trained personnel are required to operate these conventional analysis machines effectively, as a mistake in their operation can render entire sample runs useless.
In order to handle the transportation, alignment, and tracking needs of large sample batches effectively, most prior art multi-channel analyzers utilize sample tube racks or carousels which are organized and loaded with sample tubes prior to positioning within the analyzer input area. Though these racks provide a degree of convenience in connection with sample tube handling, bulk storage, and identification, they make it virtually impossible to interrupt the analyzer apparatus once a sequence has been started and also impose a degree of restriction with respect to the handling of individual sample tubes. That is, the feeding of the sample tubes is sequential, as is the generation of test results to then be correlated with the particular sample tube, and to the patient from which the sample was taken.
Another significant disadvantage associated with these types of automated analyzing equipment is their inability to perform emergency, or "stat" tests. This inability arises because of the relatively long and complex setup times and the resultant inability to interrupt the order and flow of the organized samples of conventional analyzers. Similarly, though a relatively rare occurrence, if a sample tube should fracture or leak the entire sample run may be jeopardized if the machine cannot be interrupted without losing track of the samples in and in preparation for testing.
An alternative approach to sample tube handling has been the development of individual sample tube carriers which may be stored in racks and loaded into conveyor lines. For example, U.S. Pat. No. 3,916,157, issued Oct. 28, 1975, illustrates a specimen carrier for test tubes. The carrier is provided with a slotted base engageable with a geared conveyor track for transporting the carrier through an automated analyzer. Additionally, each carrier is provided with its own identification tag so that the sample in the carrier can be identified for tracking through the analyzer. An alternative sample container is disclosed in U.S. Pat. No. 3,350,946, issued Nov. 7, 1967. This system utilizes a vial with a vertical T-shaped flange that enables it to be inserted into a carousel. A machine-readable tag is attached to the vial for tracking purposes. Similarly, U.S. Pat. No. 4,944,924, issued Jul. 31, 1990, also discloses a test tube holder that pivots along a belt-like conveyor.
Still additional sample tube conveying and sample analyzing apparatus may be seen in U.S. Pat. No. 3,762,879, issued Oct. 2, 1973. In this device, sample tubes are manually inserted into a carousel, and sample aliquots are subsequently drawn from each sample tube for delivery to plural reaction tubes. The reaction tubes are carried in transversely aligned ranks on an elongate conveyor. In this analyzer, the sequential order of sample introduction and data generation would seem to rule out the introduction of stat samples, and breakage of a sample tube could cause possible loss of correlation of generated data to the particular samples.
An alternative sample analyzer which transposes the functions of conveyor and carousel is seen in U.S. Pat. No. 3,832,135, issued Aug. 27, 1974. In this apparatus, a conveyor is manually fed sample tubes, probably from a rack of the tubes. Subsequently, aliquots of each sample are withdrawn to be supplied to cuvettes carried on a carousel. The carousel has several concentric rows of test cells in which various tests are carried out on the aliquots of sample fluid. Sample handling appears to be entirely sequential so that stat samples cannot be taken with priority without interruption of the sequences already started.
A family of analyzers which combine a plurality of carousels is seen in U.S. Pat. Nos. 4,234,540, issued Nov. 18, 1980; and 4,276,051 and 4,276,258, both issued Nov. 18, 1980. In each of these devices, a sample carousel must be fed with sample tubes, so that aliquots may be withdrawn for depositing into reaction cells carried on a respective carousel. The reagents to be used in the reaction cells are carried in yet another carousel. Again trays of samples would appear to be necessary along with manual feeding of the sample cuvettes or tubes into the sample carousel.
Yet another analyzer which combines a carousel with a conveyor of sorts is seen in U.S. Pat. No. 4,459,265, issued Jul. 10, 1984. In this analyzer, the sample tubes are retained in trays, and the trays themselves are shuttled back and forth in a recess to align particular tubes with the aliquot withdrawal station. The reaction cells are carried at the perimeter of a carousel to receive both the aliquots of sample and reagents. Processing of stat samples would seem to require interruption of the test sequences already in process.
A more recent attempt to provide the combination of functions and advantages desired in an automated sample analyzer is seen in U.S. Pat. No. 4,678,752, issued Jul. 7, 1987. This analyzer provides a conveyor and a carousel, with the latter being employed as a short term storage area. A shuttle system is employed to move the samples between the introduction area, a liquid transfer station, a detector, and the storage area. The liquid sample and the reagents to be used therewith are carried as a package into and through the machine. The necessity to provide each sample to the analyzer along with the appropriate reagents would seem to require highly skilled operators for the machine, and the time sequencing of the samples in process to the single detector via the single shuttle would seem to limit the throughput of the analyzer. The sample and reagent packages also appear to be rather large so that the size growth of the machine with increasing number of samples thereon, or the limited number of samples in its processing inventory may be a disadvantage.